Radio gun control system



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RADIO GUN CONTROL SYSTEM Filed April 30, 1942 12 Sheets-Sheet 1 I J I T SEARCH TRANSMITTER SCANNER RECEIVER INDICATOR 7 GUNS COMPUTER 1 lo fig r TRACKING TRANSMITTEn SCANNER RECE'VER INDICATOR 2 .5 9? If L 4 C 6/ GUNS COMPUTER T IN DTEE'I QR JET-3; Q

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W.W.MIEHER.& J. E.SHEPHERD) Nov. 11, 1952 c. G. HOLSCHUH ET AL 2,617,982

' RADIO GUN CONTROL SYSTEM Filed April 30, 1942 12 Sheets-Sheet 2 TRMSMTrER I osc.& MODULATOR PULSE GEN. I

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1952 c. cs. HOLSCHUH ETAL 2,617,982

RADIO GUN CONTROL SYSTEM Filed April 30, 1942 12 Sheets-Sheet 3 MINIMUM lb! INVENTORS', C.G.HOLSCHUH, G.E.WHITE w.w. MIEHE'R, & J.E.SHEPH'ERD W L/M THE-IR ATTORNEY.

1952 c. G. HOLSCHUH ETAL 2,617,982

RADIO GUN CONTROL SYSTEM Filed April 30, 1942 12 Sheets-Sheet 4 DEMODULATOR DEMODULAT VE CR8,

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Nov. 11, 1952 c. G. HOLSCHUH ET AL 2,617,982

RADIO GUN CONTROL SYSTEM Filed April 30, 1942 12 Sheets-Sheet 6 94 WIDE BAND AMPLIFIER TR -T BOX RECENER TR NS'. MOD. P I PULSE GEN- P A 2 A mupgz CONTROL T v r 2 THEIR ATTORNF Nbv; I1, 1952 c. G. HOLSCHUH ETAL 2,617,982

RADIO GUN CONTROL SYSTEM Filed April 30, 1942 12 Sheets-Sheet 7 SCANNER From I Receiver 94 Oufpuf COMPUTER SCANNER 94 RANGE From COM PU TER SERVO Receiver Oufpuf .IEFEE.

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0L THEIR ATTORNEY.

1952 c. G. HOLSCHUH El'AL 2 RADIO GUN CONTROL SYSTEM 12 Sheets-Sheet 10 Filed April 30, 1942 THEIR ATTORNEY.

Nov. 11, 1952 c. G. HOLSCHUH ETAL 2,617,932

RADIO GUN CONTROL SYSTEM Filed April 50, 1942 I 12 Sheets-Sheet 11 O i i f f l A sfiufiigr' aq Oufpu of wave B squclrer 32b i k Out u: of C p generez fgf 32c I88 I F 1 Rudiaied ulse D [88 enve ope -r |9l I 2 E lnpul' #0 T4? box 33 O f i f v F u pu sqg ye r I93 l I i Ji s Oulpuf of wave 6 squarer I97 I i ,-2o|

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INVENTORS' C.G.HOl -SCHUH, G.E.WH|TE, EEEr-E A W.W.M!E HER a. J.E.SHEPHERD;

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THEIR ATTORNEY.

RADIO GUN CONTROL SYSTEM Filed April 30, 1942 12 Sheets-Sheet l 2 Wide gafe Receiver wide channel oufpuf Range index square wave Na rrow gaie Oufpul of receiver narrow channel Oaipui of signal siorer Sweep volfage Ouipuis of iniensifiers I &]I

Ranqie index wave Orieniah'on .ingiicaiion perno Range indica'rion perlod INVENTORS. J5 &=3E c.e. HOLSCHUH, G.E.WH|TE,

MIE HER,8. J E SHEPHERD;

THEIR ATTOP NEY.

Patented Nov. ll, 1952 UNl RADIO GUN CONTROL SYSTEM Carl G. Holschuh, Glen Head, Gifford E. White, Hempstead, Walter W. Michel, Mineola, and James E. Shepherd, Hempstead, N. Y., assignors to The Sperry Corporation, a corporation of Delaware Application April 30, 1942, Serial No. 441,183

63 Claims. 1

The present invention is concerned with radiodirected fire control systems especially adapted for use in aircraft and against other fast moving aircraft.

For the protection of large aircraft, such as heavy bombers, it is known to use flexible gun turrets movable independently of the craft in association with a computing gun sight or computer which is manually tracked with the target and thereby derives the proper gun aiming data for controlling the gun turrets. Up to the present time, however, such inter-aircraft fire control devices, and also anti-aircraft fire control devices, have relied upon visual tracking of the target for determining the correct gun aiming angles. Such prior art systems are subject to the well known limitations of visual sighting, such as reliance upon proper weather and visibility conditions, upon sufhcient lighting, and upon the restricted range of optical telescopes. Even under optimum conditions of visibility, the visual detection of the approach of aircraft and visual tracking with aircraft have been difiicult and uncertain. For instance, aircraft approaching from the direction of the sun can be seen only with the greatest diificulty. Furthermore, the observer cannot scan the whole zone of danger quickly and carefully with certainty by the eye alone.

In order to overcome these and other disadvantages of the prior systems, the present invention provides a system in which the target is detected, located, and tracked by a radio beam Which effectively replaces the visual line of sight of prior systems. However, before describing the present system, certain essential requirements for such a system will be discussed.

Firstly, the defending aircraft must be apprised of the presence and approximate direction or orientation of all targets in its vicinity in order to be able to efiectively plan and accomplish its defense. In addition, it is desirable that the approximate range of each of these various targets should be indicated simultaneously with its location, for similar reasons. After having been warned of the presence, orientation, and range of these targets, and after having chosen one or more of them as of greater importance for immediate engagement, it is necessary for the particular target selected to be u tracked by the ire control system in order to determine the target present position, such as defined by is elevation, azimuth, and range, in the present case, and to determine the rate of change of position, as defined by target elevation rate and azimuth rate, in order that the correct gun aiming angles for controlling the guns and turrets may be derived by the computer.

In order to relieve the fire control officer of as much of the burden of tracking as is reasonably possible, it is desirable to automatically track with the target, at least in elevation and azimuth, and possibly also in range, so as to automatically set into the computer mechanism the proper target position and target rate data.

The present system offers an improved type of v warning or searching system in combination with several types of tracking or fire control systems. Preferably, since space and weight are at a premium in aircraft, these various systems are combined as much as possible to use a minimum amount of equipment.

Accordingly, by the present system there is provided apparatus for indicating the presence, approximate orientation, and approximate range of all targets within a predetermined portion of space, such as a hemisphere, which apparatus may be converted upon selection of a particular target into any one of three different types of tracking systems: (1) a system in Which the fire control oificer actuates the computer setting in such a manner as to maintain a radio line of sight in track with a target, (2) a system in which a radio line of sight is automatically tracked with a target and the fire control oil-leer actuates a computer to maintain it in synchronism with the radio line of sight, and (3) a fully automatic system in which a radio line of sight is automatically maintained in synchronism with the target and serves to automatically set into the computer the proper target data required by the computer.

By such a system both the warning and tracking may be performed entirely independently of any optical visibility conditions and at a much greater range than was formerly possible, without impairing in any Way any of the desirable features of former types of fire control systems.

In addition, the operation of the present systern is made to agree in substantially all operations to be performed with the operation of prior systems and the natural instinctive reactions of the operator are utilized by the provision of controlling operations which are naturally dictated by the circumstances encountered.

Accordingly, it is an object of the present invention to provide improved gun control systems independent of visual devices.

It is another object of the present invention for providing improved radio-operated gun control systems.

It is still another object of the present invention to provide improved radio-directed gun control systems for detecting the presence of a target and for tracking a computing gun sight with the target.

It is still a further object of the present invention to provide improved automatic gun control systems.

It is still another object of the present invention to provide improved object detecting and locating devices.

It is a further object of the present invention to provide improved warning systems adapted to indicate the presence, location and approximate range of distant objects.

It is yet another object of the present invention to provide an improved gun control system adapted to selectively (a) search and locate targets, (b) manually track with targets, semiautomatically track with targets, or (d) fully automatically track with targets.

It is another object of the present invention to provide improved devices for indicatin e tive displacement between the orientation of a distant object and a predetermined axis such as a radio line of sight.

It is a further object of the present invention to provide improved devices for setting a member, such as a range control member of .a computer, in accordance with the distance or range to a distant object.

It is still a further object to provide improved apparatus for automatically maintaining a predetermined axis oriented toward a fast moving target.

Other objects and advantages of the present invention will become apparent from the following specification and drawings, in which,

Fig. 1 shows a black or flow diagram of the system of the invention during searching operations.

Fig. 2 shows a corresponding block diagram of the system during manual tracking operations.

Fig. 3 shows .a corresponding block diagram of the system during manual automatic operations.

Fig. 4 shows a block diagram of the system during full automatic operations.

Fig. 5 shows a schematic perspective view of one form of scanner useful in the present system.

Fig. .6 shows the radiation pattern of the directive antenna array used with the scannerof .Fig. 5.

Fig. 7 shows .a longitudinal cross-sectional view of the radiation pattern of the scanner of Fig. 5 during any .of the tracking operations.

Fig. 7A is .a cross-section of Fig. 7 taken along lines 1A-1A thereof.

Fig. 8 shows a schematic block wiring diagram of one form of radio transmitting, receiving and indicator circuit for searching operations.

Fig. 8A shows a representative view of the cathode ray screen of the indicator of Fig. 8.

Fig. 9 shows a schematic circuit diagram .of the spiral sweep or reference voltage generating apparatus for the circuit of Fig. 8.

Figs. 10A, 10B, 10C, and 10D are voltage-time graphs useful in explaining the operation of the circuit of Fig.9.

Fig. 11 shows a modification of a portion .of the circuit of Fig. 9 to the right of line AA thereof.

Fig. 12 shows a further modification of the spiral sweep or reference voltage generating apparatus of Fig. 9.

Fig. 13 shows a modification of th circuit of Fig. 8, including simultaneous range indicating means.

Fig. 13A shows a representative view of the cathode ray screen of the indicator of Fig. 13.

Fig. 14 shows voltage-time graphs of various portions of the circuit of Fig. 13.

Fig. 15 shows a modification of the portion of the circuit of Fig. 13 within dotted enclosure B.

Fig. 16 shows corresponding voltage-time graphs referring to the circuit of Fig. 15..

Fig. 17 shows a block circuit diagram of one form of apparatus for controlling the scanner orientation from the computer setting, as during searching or manual tracking operations.

Fig. 18 shows a block circuit diagram of one form of range indicating system.

Fig. 18A shows a representative indication produced by the system of Fig. 18.

Fig. 19 shows a modification of the range indicating system .of Fig. 18.

Figs. 19A and 193 show alternative types of indication produced by the system of Fig. 19.

Fig. 20 shows a block circuit diagram of one form of indicator useful during tracking operations.

Fig. 20A shows a representative indication produced by the circuit of Fig. 20.

Fig. 21 shows a modification of the indicating system of Fig.20.

Fig. 21A shows a representative indication produced by the circuit of Fig. 21.

Fig. .22 shows a modification of the portion of the circuit of Fig. .21 to the right of line C--C thereof.

Fig. 23 shows another modification of the circuits of Figs. 20, 21, and 22.

Fig. 23A shows a representative indication produced by the circuit of Fig. 23.

Fig. 24 shows a block circuit diagram of .a further indicating system useful during tracking and incorporating several of the features of Figs. 20 to23.

Fig. 24A shows a representative indication produced by the circuit of Fig. 24.

Fig. 25 shows a schematic block diagram of the scanner control and indicator for semi-automatic operations.

Fig. 26 shows a schematic block diagram of the computer setting control for full automatic operations.

Fig. 2'7 shows a block circuit diagram of an indicator system combining range and orientation indications upon a common indicator and useful for searching or any form of tracking.

Fig. 28 shows a schematic block diagram of a scanner and computer control adapted for any one of the four types of operation.

Fig. 29 shows .a schematic perspective view of .a manual control unit suitable for use in Fig. 28. Fig. 30 shows a radio and indicator block circuit diagram adapted for selectively producing any one of the four types of operation.

Fig. 31 shows voltage-time curves of various parts of the circuit of Figs. 29 and 30 during searching operations.

Fig. 32 shows corresponding voltage-time curves during tracking operations.

As discussed above, the present system is adapted for two major types of operation, namely, (l) a searching operation for roughly indicating the position and/or distance of any targets within the field of operations of the device and (2) a tracking operation in which a particular target .may be selected and followed by the device for properly directing a gun thereat. Three alternative types of tracking operation, known as manual, semi-automatic, and full automatic tracking may be used.

For describing generally these various types of operation, recourse is had to Figs. l-4, more specific detail of the system being described with respect to later figures.

Fig. 1 shows a block or ,flow diagram of the present system when operating during searching. In this system, a scanner l projects a sharply directive beam of radiant energy, such as 19 in Fig. 6, obtained as from a suitable transmitter 2 and directive antenna arrangement 3. This beam comprises a periodic sequence of short duration pulses of high frequency energy, and during searching is swept in a spiral cone over a predetermined solid angle, which is preferably substantially a hemisphere, in such manner that the radiant energy is projected at some time during its cycle into every part of the solid angle. Should any object or target be located in this solid angle, the projected radiant energy will be reflected therefrom when the beam is directed thereat, and will be received in the same antenna system 3, which acts dually as a transmitting and a receiving system.

This reflected series of pulses of high frequency energy is received in a radio receiver 4 whose output actuates a suitable indicator 6. This indicator, as will be described below more in detail, is preferably a cathode ray tube whose electron beam trace is caused to sweep in spirals in synchronism with and instantaneous correspondence with the spiral scanning motion of the scanner. For this purpose the indicator 6 is also controlled from scanne 1. The received reflected pulse is caused to momentarily brighten the trace of the beam and thereby produce on the cathode ray screen an indication of the existence and approximate orientation of the reflecting object. The approximate range of the reflecting object may also be shown, as described below with respect to Figs. 13-16.

Th orientation of the scanner I, which may be taken to be the orientation of the polar axis of the spiral conical scanning motion, is placed under the control of a computer 1, whose elevation and azimuth settings may be manually actuated from a suitable manual control 8. Computer i is adapted to calculate the proper gun aiming angles for intercepting the target by a projectile when the computer is set in accordance with the present target position data, such as elevation, azimuth and range of the target, and in accordance with the rate of change of the present target position, such as elevation rate and azimuth rate. A suitable form for such a computer is shown more in detail in copending application Serial No. 411,186, for Inter-aircraft Gun Sight and Computer, filed December 17, 1941, in the names of C. G. Holschuh and D. Fram, now abandoned. As is shown in this copending application, the range setting of computer '1 may be performed by a suitable foot pedal it. The orientation control is effected by a handle bar control 3 whose displacement about two independent axes represents a combination of the displacement and rate of change of displacement of azimuth and elevation settings of computer i, providing aided tracking. In operation, the controlling oiiicer actuates control 8 so as to maintain the present target position setting of the computer i in track with the target, as evidenced (in the prior application) by a suit able optical sighting arrangement. By so doing, the proper target elevation, target azimuth, target elevation rate and target azimuth rate are set into the computing mechanism l together with the range data set in by foot pedal I 0, whereby computer 7 may determine the gun aiming angles. In the present system, the same operations are performed, but utilizing a different type of indicator to show the proper tracking conditions, as will be described.

The scanner I is suitably controlled, as will be een hereinafter, in accordance with the target elevation and target azimuth setting of computer i. The gun aiming angles determined by computer 'l' are used to suitably control the orientation of one or more guns or turrets 8, which are thereby rendered effective against the target.

A suitable type of gun control apparatus for orienting the guns 9 under the control of the computer I is shown in copending application Serial No. 424,612, for Hydraulic Remote Operating Systems, filed December 27, 1941, in the names of E. L. Dawson, F. M. Watkins and C. N. Schuh, Jr., which issued on July 27, 1948 as U. S. Patent No. 2,445,765. It is to be noted that the present system is not confined to the use of this particular type of gun control apparatus, but that any other suitable type of remote control system may also be used. If desired, the guns 9 need not be directly controlled from computer 1 but may be locally controlled in accordance with suitable indications transmitted from corn puter 1 in any well known manner.

The system as shown in Fig. 1 is not intended for use as the actual gun control system but is merely intended to search out possible targets and to enable the scanner to properly locate a target for the purpose of later tracking with it. For thisreason, the control from computer i to guns 9 is shown dotted in Fig. 1. After a target is observed on the screen of cathode ray indicator 6, the manual control 8 of computer 'i is actuated to adjust the orientation of scanner 1 to the position where this orientation coincides as closely as possible with the orientation of the desired target, as evidenced by the position of the bright spot indication on the indicator screen. When this adjustment has been made, the system is ready to change-over to the tracking operation.

The present system is adapted to use three separate and distinct types of tracking, any one of which may be selected at the option of the fire control ofiicer. It is to be noted that each of these types of tracking system may be used independently of the others if desirable. For all of these types of tracking operation, scanner 1 is energized from transmitter 2 by the same type of periodic pulse wave as described with respect to the searching operation. However, scanner I no longer performs spiral scanning as in Fig. 1 but instead it is converted to perform a narrow circular conical scanning with a very small apex angle. Preferably, this angle is of the order of the angular width of the radiation and reception pattern derived from antenna 3, indicated in Figs. 6, '7 and 7A.

Thus, if antenna system 3 is adapted to produce a beam of radiant energy having a directive radiation pattern such as E9 in Fig. 6 with a directivity axis 25 then, during tracking, beam it will be rotated by scanner 1 about an axis such as 23 in Fig. '7, whereby directivity axis 2! performs a conical motion about axis 23, which may be termed the tracking directivity axis since it is this axis which defines the radio line of sight, as will be seen. Preferably, radiation pattern i9 is made to have a small apex angle such as of the order of 4 in angular width between the halfpower points. Then, during tracking, the cone described by axis 2i Would preferably have an apex angle also of the order of 4. In this manher, the useful portion of the radiant energy would be projected over a conical solid angle having an 8 apex angle. Energy reflected from an object or target within the field of this radiant energy will be received by antenna arrangement 3 and led thereby to receiver 4 whose output actuates the tracking indicator E to indicate the relative displacement between the scanner orientation defined by axis 23 and the orientation of the target.

In the system of Fig. 2, manual actuation of computer control '8 serves to set azimuth and elevation .data into computer] and at the same time controls the orientation of scanner I, as determined by axis 23, to assume the same azimuth and elevation-as is set into computerl, in the same manner as described with respect to Fig. 1. In effect, the orientation of scanner I ismade the same as the orientation of computer I, the latter term meaning the orientation corresponding to the azimuth and elevation data set into the computer mechanism.

Also actuated from receiver 4 is a range indicator 6". A matching index is provided for indicator 6", as will .be described more in detail below, which is placed under the control of range pedal I8 serving also to set range data into computer :I.

In operating the system of Fig. 2, the operator will, by his manual control 8, orient scanner I until the tracking indicator 8' shows that the target orientation coincides with the scanner orientation. At the same time, the operatoractuates the range foot pedal It to match the range index to the indication produced by range indicator 6"; When these conditions obtain, and are maintained even during the motion 01 the target, the operator will know that the proper data is set into computer -'I and that the guns 9 controlled from the computed output of computer I are-directed at the correct aiming angles to intercept the target with a projectile, and he may therefore, by a suitable firing key or control, fire at the target.

This system is known as manual tracking since the operator, through his manual control 8 and foot pedal I0, directly actuates the scanner and computer I to track with the target as evidenced by indicators 6' and 6". The scanner I, in effect, operates to produce a radio line of sight in the same way as the sighting telescope in a conventional anti-aircraft or inter-aircraft system operates to produce an optical line of sight, to enable the computer I to track with the present position of the target, whereby the preper gun aiming angles are determined.

A second type of tracking operation is illustrated in Fig. 3 and is termed semi-automatic tracking. In this case the scanner 'I, again performing circular conical scanning as described with respect to Fig. 2, is caused to automatically align its orientation with that of the target. This is done by using the reflected pulses received from the target to actuate suitable servomotors for orienting the scanner, which is thereby automatically oriented toward and tracks with the target. The computer I is again manually controlled from controls 8, in this instance to follow and track with the orientation of scanner I. Thus, tracking indicator 6' in this type of system serves to indicate the displacement between the orientation of scanner 1 and computer I, and computer 'I is actuated to maintain this computer error at zero. When this condition obtains, and with the proper computer range ad justment, similar to that described in Fig. 2, the output of computer I, controlling guns 9, again represents the proper gun aiming angles and efiective fire may be obtained from the guns.

Fig. 4 shows the third or full automatic tracking system in which no manual actuation is necessary. Here, scanner I is automatically oriented toward the target, under the control of the output of receiver '4, as in Fig. 3, and, in addition, the orientation of computer 'I is caused to automatically follow the position of scanner I by a suitable servo mechanism. In this manner, the .proper target azimuth and elevation data .are set into the computer I. The range adjustment of computer I is also automatically performed b a range control Iii under the control of receiver '4. This system, however, does not obtain the target rates, that is, elevation rate and azimuth rate, in the same manner as in Figs. 2 and 3.

In the system of Fig. 4, it-is necessary to determine elevation rate and azimuth rate by actuallymeasuring the angular rate of motion of the azimuth-and elevation input controls of scanner I. This may be done in any well known Way, such .as-is shown and described in U. .8. Patent No. 2,206,875, for Fire Control Device issued July 9, 1940 in the name of E. W. Chafee et al. In this manner, all the required data may be set into computer "I and therefore the guns 9 are automatically oriented at the propergun aiming angles and automatically follow the target with, of course, the computed lead angles.

Indicator 6 in this instance merely serves as a monitor indicator to show how well the scanner l is following the target or, alternatively, how well the computer I is following and tracking with scanner I. Indicator 6" serves similarly as a range monitor indicator.

The present system is therefore capable of four alternative modes of operation, namely, searching, manual tracking, semi-automatic tracking, and full automatic tracking.

Fig. 5 shows aschematic representation of one suitable type of scanner I. Thus, the scanner I may comprise a directive antenna system 3, shown as comprising a parabolic wave guide reflector, and energized through suitable electromagnetic wave guide connections II from transmitter 2. A suitable construction for scanner I is shown and described in copending application Serial No. 438,388, for Scanning Devices, filed April 1-0, 1942 in the names of L. A. Maybarduk,

VT. W. Mieher, S. J. Za-nd and G. E. lVhite, which issued on November 12, 1946 as U. S. Patent No. 2,410,831. As therein disclosed, the antennaarrangement 3 in one form may be continuously nodded or oscillated at a slow rate about nod axis I2 which is itself rapidly and continuously rotated 0r spun about spin axis I3 thereby producing a spiral conical scanning pattern by the continuous widening of the conical sweeping about spin axis I3. To convert rom the spiral searching scanning to the circular tracking scanning, the nod motion about the nod axis I2 is interrupted, with the orientation of the directive radiation or receptivity pattern axis 2| displaced slightly from the spin axis I3.

In order to feed radiant energy from wave guide II to the radiator 3, suitable stationary joints I I and rotatin joints IS are provided as described more in detail in the above-mentioned copending application Serial No. $38,388, and in copend-ing application Serial No. 447,524 for high irequency apparatus, filed June 18, 1942 in the names of W. W. Mieher and J. Mallet, which issued on September 10, 1946, as U. S. Patent No. 2,407,318.

To provide the necessary control of tracking indicator 6 from scanner I, in the manner to g. be described, suitable self-synchronous position transmitters are provided for producing signals indicative of the instantaneous position of the radiator 3 in nod and in spin, that is, indicative of the orientation of axis 2|. The nod transmitter is indicated schematically at I1, the spin transmitter at 18. These transmitters may be of the well known Selsyn, Autosyn, or Telegon types.

Referring to Fig. 6, there is shown the radiation or receptivity pattern IQ, of the antenna array 3 of Fig. 5. It will be noted that this radiation pattern i9 preferably is axially symmetrical about axis 2!, and is substantially contained within a narrow solid cone 22, thereby forming a sharply directive beam of transmitted energy or a sharply directive reception pattern. Pattern l9 has been exaggerated for purposes of illustration, and preferably is very narrow, such as about 4 between the half-power points. During searching operations the axis 2| of this beam 58, by virtue of the combined effect of the nodding and spinning action of scanner 1, is caused to sweep out a spiral cone in space, the solid angle of this sweep being suitably chosen and ranging up to a complete hemisphere as desired. Preferably, the angular pitch of this spiral is chosen to be of the order of the effective angular width of the beam I9 whereby, during one complete spiral scan every portion of the conical solid angle will have had radiant energy projected to it, and radiant energy may be received from every such portion. The rates of nod and spin of the scanner of Fig. 5 are suitably chosen to provide a sufiiciently short time interval for a complete scan, suitable for the purposes at hand.

Durin trackin operations the nod motion of scanner l is stopped at a position so that the axis 2! of maximum radiation or receptivity is displaced slightly from the spin axis l3 about which the radiation pattern I 9 is rotated. In this way, as shown in Figs. 7 and 7A, energy of constant intensity is radiated or received along an axis 23 coincident with spin axis 13. However, along some other axis, such as 24, for example, maximum radiation and maximum receptivity is encountered only once during each spin cycle, resulting in a spin frequency modulation of waves received by reflection from an object orientated along axis 24.

The use of the same antenna arrangement for transmitting and receiving increases the sharpness of the resulting determinations since the over-all response pattern is the product of the radiation and receptivity patterns. If desired, however, a non-directional transmitter or receiver could be used with the described scanner acting respectively as a receiver or transmitter.

Conversion from searching to tracking scanning is effected, as described in application Serial No. 438,388, merely by energization of a suitable control solenoid. Other types of scanners are also described therein, requiring different apparatus for converting from searching to tracking, but all adapted to be used for searching or tracking in the same manner as the scanner of Fig. 5.

t may also be desirable to adjust the axis of this spiral scanning during the searching operation. For this purpose, scanner 1 may be provided with an elevation axis 26 and an azimuth axis 21 about which it may be suitably adjusted, in the manner described in application Serial No. 438,388, the control action being as described below. Also, suitable elevation and azimuth posi- 10 tion transmitters 28 and 29 may be used, as will also be described below.

Fig. 8 shows one form of radio and indicator system for giving suitable indications during searching. Thus, assuming that the scanner of Fig. 5 is performing the spiral scanning described above, antenna array 3 is fed with radiant energy as over wave guide H, from a transmitter and modulator unit 3 I. This transmitter 3| is adapted to produce high frequency radiant energy in any Well known manner, and to modulate this high frequency energy by means of periodically recurring short duration pulses such as may be derived from a conventional control oscillator and pulse generator 32. There is thus radiatedfrom the radiating arrangement 3 a sequence of short pulses of high frequency radiant energy. The frequency of control oscillator 32 and thereby the repetition frequency of the radiated pulses is chosen to have a suitably, high value such that a substantial number of pulses is sent out during each spin rotation of the scanner I of Fig. 5. Suitable values for various constants of the circuits during this form of operation have been found to be the following: spin rotation, 1200 revolutions per minute; nod oscillation, 30 complete oscillations per minute; pulse repetition frequency, 2000 per second. With these values it will be seen that one complete cycle of spiral soanning will be accomplished each two seconds, one second being taken up in a spiral scan from zero nod to full nod, the other second of the cycle comprising the time for spiral scanning from full nod back to zero nod. During each half of the complete cycle 23 complete spin rotations are performed. Thus, for a full hemisphere of scan, the angular advance for each spin cycle will be approximately d degrees, which is of the order of magnitude of the width of the radiation pattern i9 shown in Fig. 6. The pulse repetition rate of 2000 pulses per second gives pulses per spin rotation, which thereby produces one pulse for each 3.6 degrees of motion of the radiation pattern l9 during scanning. Since the radiation pattern 59 is approximately 4 to 5 degrees wide, it will be seen that at least one pulse of radiant energy is transmitted to each point of the hemisphere.

Should a distant object be in the field of the system during radiation, at least one pulse will be incident thereon, and reflected therefrom. This reflected pulse or pulses will be picked up in the antenna arrangement 3 and conducted through wave guide H to the receiver unit t through a T-R box 33. T-R box 33 is adapted to pass the relatively low intensity received pulses but to block out the relatively high intensity transmitted pulses derived from transmitter 3i. A suitable form for such a T-R box 33 is shown in copending application Serial No. 406,494 for Radio Apparatus for the Detection and Location of Objects, filed August 12, 1941 in the names of J. Lyman et al., and comprises, as is therein shown, an ionizable medium containing a spark gap within a resonant cavity which is resonant to the high frequency of transmission. The spark gap is so adjusted that the low intensity received waves are insufficient to create a discharge across the gap, whereas the high intensity transmitted pulses are sufilcient to create such a discharge, which thereby ionizes the ionizable medium and effectively short circuits the wave guide l l to these transmitted waves. In this manner the receiver unit 4 is effectively isolated from the high intensity transmitted pulses while being free to receive the pulses reflected from a distant object. Receiver unit includes conventional pro-ampliiying, detecting and wide-band amplifying units, all well known in the art, and is adapted to prcduce, in its output, signal currents or voltages corresponding to the wave shape of the envelope of the received reflected wave.

Referring to Fig. 1d, the wave envelope of the radiated waves may be as shown at 3A. The output of receiver unit 4 (see Fig. 13) may then have the wave shape shown at 36. As there shown, a plurality of reflected pulses, 36a, 36b, etc., have been received corresponding to a plurality of reflecting objects located along the particular orientation of the radiation and reception pattern at the instant under consideration. These pulses are applied to the control grid 3'! or the cathode ray tube indicator 6 shown in Fig. 8. Grid 3's is provided with a suitable bias, as by way of lead 38, such that, with no output from receiver 4, the cathode ray beam, produced by the usual means, is prevented from reaching the screen of the cathode ray tube indicator 6. However, this bias'is also so adjusted that the received pulses 36 derived from the receiver unit 4% are permitted to momentarily render the electron beam trace visible on the screen of indicator 6. Thus, it will be clear that each time a reflected pulse is received a momentary bright spot occurs on the cathode ray screen.

In order to give an indication of the orientation of the reflected object with respect to the location of the system of the invention it is desirable to produce a spiral scanning of the electron beam in synchronism with and corresponding instantaneously to the spiral scanning of the radiation and receptionpattern I9, Suitable devices for obtaining deflecting voltages which will produce such a spiral scanning areshown in Figs. 9 through 12. Assuming, for the moment, that such spiral sweep voltages, designated as P1 and P2, have been obtained, these voltages P1 and P2, to be hereafter described more in detail, are im.- pressed upon respective pairsoi deflecting plates of the cathode ray indicator 6' and produce a spiral scanning ofthe electron beam such that, at

each instant the orientation of the latent trace of the beam on the screen. of the cathode ray indicator 6 with respect to the screen center or pole 39 of Fig. 8A, corresponds to the instantaneous orientation of the beam axisil of antenna array 3 of scanner I-. Under these conditions the momentary brightening or intensifying of the electron beam underv the control of receiver 4 will produce a momentary bright spot such as 4| shown in Fig. 8A If a plurality of objects having difierent orientations are within the efiective field of the searching system further bright spots such as 42 audit will also be produced, each having an orientation with respect to, pole 38 respectively corresponding to the orientation of the corresponding reflecting object with respect to the spin axis I3 of the scanner 1.

As described above, the transmitted pulses and hence the reflected pulses are of quite short duration, such as the order of l microsecond. In order that the brightspots M, 42 and 43. may be more clearly shown it is desirable to let the beam impinge upon the screen for a longer interval. For this purpose a signal storer M is inserted between receiver 4 and intensity control grid 31. This signal storer 44 may simply comprise a condenser-resistor network adapted to be instantaneously charged by a pulse derived from receiver 4 and. which will maintain its l2 charge beyond the duration or the pulse. How-'- ever, the time constant of the signal storer 44 is preferably so chosen that this accumulated charge will be fully dissipated within atime not much longer than one recurrence period oi the transmitted pulses in order that erroneous indications shall not be obtained. In this way the traces ,5], 52, 43 are made brighter. In addition, the screen of indicator 6 is preferably made of high retentivity, so as to maintain its indication for a substantial interval after excitation is removed.

Fig. 9 shows one form of circuit for producing the spiral sweep voltages 561 with indicator 6 of Fig. 8. In this figure, nod transmitter I! is indicated as being of a two-phase type having a single-phase energizing winding 46 and a, two.- p as da y in n 41, in t is instanc connected in series to provide a single output. n n 6 s i d fr m a suitab e sourc 43 of alternating current, The outputv voltage appearing ac s e no phase Winding 41. namely ta V hav n w shape asshown in Fig. 10A, will therefore be an alternating l a e hav n th fr quenc of source 48 and an amplitude varying in correspondencewith the unt of r rr sito th or n at on of the an er p n ax s as z ro Qdh w ve is, wn n H s 9 bei llustrated as, havin a linear change of amplitude with nod; It, is to be noted that ordinarily thisichange of, amplitude will be sinusoidal in character. How ever, by the use of proper motion convertin devices whereby full nod motion corresponds to a small angular displacement of winding 46. with respect to winding 41, it may be made linear as illustrated. Preferably full nod ismade to, correspondto less than 45 rotation of transmitter l1, resulting thereby in: substantially linear output as shown in Fig. 10A.

During searching operations, switch 49. will be connected to terminal S and hence the output voltage V1 of nod transmitter H is fed to the single-phase winding 5|. of the spin. transmitter 18. Theoutput from each of the two-phase windings 52 and 5.3 of spin transmitter l8.will then be the wave of Fig. 10A sinusoidally mod.- ulated in amplitude at the frequency of; spin. This is shown in Fig. 10B. for the winding 52. The winding 53,, being displaced in space with respect to winding 52,, will-have induced in it a voltage of similar wave shape but displaced 90 in phase at the spin. frequency. Ineffect, spin transmitter [8 serves asa two-phase, gene erator of spin frequency whose output. amplitude is controlled by nod. transmitter II.

To each of. these, voltage outputs windings 52 and 5.3.there is adde a voltage. o f-the frequency of source 18, as by way of transformer 54, pro: ducing the wave shown in Fig. 106. It is toibe noted that the wave of Fig. 'lo-Brepresents in ef feet a suppressed-carrier modulated wave. The reinsertion of the carrieras by transformer produces the usual modulated. carrier'wave-shown in Fig. 100. The resulting two waves are then rectified or detected in respective rectifiersiiiv and 51 and filtered in filters 58 and; 59 to'produce the output voltages appearing on. output, leads 6! and 62 having'the wave shape shown in Fig. 10D, namely, phase-displaced voltages. of spin frequency modulated by' the nod wave envelope.

These two voltages appearing on. lines BI and 62 will be phase displaced by 90 of the spin frequency. They will be termed the spiral sweep voltages P1 and P2, respectively. As is well known, if two voltages of equal amplitude and frequency, phase displaced by 90, are impressed on the respective pairs of deflecting plates of a cathode ray tube, the resulting trace of the electron beam will be circular. By simultaneously varying the amplitudes of the two voltages the diameter of the circle will be varied.

In the present instance, by using the two waves P1 and P2 as the deflecting voltages, the beam will be caused to produce a circular pattern of constantly changing diameter and will thereby produce a spiral pattern similar to the pattern swept out in space by the scanner I. It will, therefore, be clear that these voltages P1 and P2 are particularly suited for use in indicator 6.

During any of the three types of tracking, nod transmitter H is disconnected from spin transmitter 18 by switch 49, which then connects winding 5! of spin transmitter [8 to a fixed source of alternating voltage, such as source 48, as by way of lead 56. In this case, output sweep voltages P1 and P2 will have constant amplitude, producing a circular trace on indicator 6, and accordingly will be termed circular sweep voltages.

Fig. 11 shows an alternative circuit for inserting the carrier and demodulating the waves produced by spin transmitter [8 to produce the sweep voltages P1 and P2. Thus, here the respective outputs of windings 52 and 53 are impressed upon the grids of respective detector or demodulator tubes 63 and 64 whose plate circuits are energized simultaneously from alternating voltage source 48. By properly phasing the anode voltage with respect to the grid voltages, and by filtering out all carrier frequency components, as in filters 58 and 59, the same type of spiral sweep voltages P1 and P2 will be obtained as in Fig. 9.

Fig. 1 shows a further modification of the spiral sweep voltage generating circuits of Figs. 9 and 11, particularly adapted for using conventional autosyn or selsyn devices. Thus, the nod transmitter I? comprising, as is well known, a three-phase type winding 47 and a singlephase winding 48' relatively rotatable with respect to one another, has two of its polyphase field windings energized in series from the source 48 of alternating Voltage the third winding remaining unenergized. In efiiect, therefore, there is produced in the single-phase winding 66' a varying alternating voltage similar to the voltage V1 shown in Fig. 10A. It will be apparent that nod transmitter ll of Fig, 9 and transmitter ll" of Fig. 12 are completely interchangeable, since, as used, they produce the same voltage output. This voltage derived in winding 36' is fed to the single-phase winding 51' of the selsyn type spin transmitter. There is thereby produced in the polyphase windings 52', 53', I8 and 55' three voltages of the character shown in Fig. 105, relatively displaced 120 with respect to one another and thereby forming a threephase spiral sweep voltage. This three-phase voltage is converted into a two-phase voltage in a conventional Scott T transformer 65, which is well known in the art. The two-phase voltage output of transformer 66 is combined with a carrier voltage derived from source 48 by way of transformer 5-4, identical to that in Fig. 9 and the resulting voltages are each demodulated in respective demodulators 6! and 68 of any well 14 known type, to produce the required sweep voltages P1 and P2 as before.

Here again means are provided for converting voltages P1 and P2 from spiral sweep voltages to circular sweep voltages. This means comprises switch 35 which connects winding 5i of spin transmitter 13 to nod transmitter I'l' during searching, and to a fixed source 48 during tracking.

Fig. 13 shows a modification of the searching indicating circuit of Fig. 8, including a rough range indication. As in Fig. 8, control oscillator and pulse generator 32 controls transmitter and modulator unit 3! to produce periodic pulses of high frequency energy, which are then radiated from the scanner l of Fig. 5, performing spiral scanning as before. The wave envelope of the energy radiated may be as shown by curve 34 in Fi 14.

Should any objects be present in the field of the radiating system, such distant objects would reflect pulses as before and the reflected pulses, having, for example, the wave shape such as at 36 in Fig. 14, would be received by the receiver t through the T-R, box 33 and would control the intensity grid 31 of the cathode ray indicator as in Fig. 8. A switch 69 may be provided, in whose upper position a signal storer id similar to that in Fig. 8 is rendered effective, while in the lower position signal storer id is cut out of the circuit, and the pulses 35 directly control the intensity grid 31.

In order to provide a rough range indication, the transmitted pulses obtained from transmitter-modulator 3! are also fed to a suitable rectifier, such as a diode ll, and the rectified pulses thereby obtained serve to excite a resonant circuit comprising a condenser 12 and a suitable inductance I3. The resonant frequency of resonant circuit l2, I3 is made fairly high, such as of the order of three megacycles, and the output of resonant circuit E2, 13, as derived from a coil M coupled to inductance i3 is caused to be damped by means of a shunt resistor 16 connected in shunt with condenser '12 and inductance 13, or by the internal resistance of inductance 73.

As a result, the voltage derived in coil 74 will have some such wave shape as shown at T! in Fig. 14. As there shown, the oscillatory wave 7? is damped so as to have substantially zero amplitude by the time the next transmitted pulse is derived, at which time a new train of highly damped oscillations is initiated. If desired, wave Ti could be even more highly damped to insure its dying out before the next transmitted pulse occurs. This damped oscillatory voltage l? is connected in series with one of the pairs of deflecting plates of cathode ray tube 6. Both pairs of deflecting plates are also energized in accordance with the spiral sweep voltages P1 and P2 as in Fig. 8,

The result of this additional voltage TI is to produce, instead of a bright spot such as M, 42 or 43 of Fig. 8A, a definite line such as 4|, 42' and d3 of Fig. 13A. The width of each of these lines depends upon the instantaneous amplitude of the wave H at the instant that the beam trace becomes visible, that is, at the instant that the received pulse such as 36a is received. It will be clear that the sooner pulse 35a is received after transmitted pulse 34 is omitted, the greater will be the instantaneous amplitude of wave '11 and therefore the longer will be the line segment indication such as ll. Since the distance to the reflecting object is directly proportional to the delay time between transmitted and received pulses, it will be clear that the closer the reflecting object is to the transmitter, the longer will be the indication shown in Fig. 13A, and the more distant the reflecting object is the shorter will be the indication. There is thus provided a rough range indication superposed on the object detecting indication of Fig. 8A resulting in the indication represented by Fig. 13A, showing the orientation and rough range of several objects in the scanning field.

The indication of Fig. 13A will be obtained whether or not signal storer 44 is used in Fig. 13. However, it is preferable to insert signal storer 24 in the circuit in order to enhance the brightness and legibility of indication. The eiiect of signal stcrer 45. is to leave the electron beam on from the instant of reception of pulse 3541 until substantially the next transmitted pulse. When such is the case, it will be clear that the indication will be in effect a bright spot similar to 41 carrying fainter wings which form the complete indication shown at M. These wings are produced by the limits of the oscillating excursions of the beam caused by voltage 11, and their length is inversely proportional to the range of the distant object.

Fig. 15 shows a modification oi the portion of the circuit of Fig. 13 contained within dotted enclosure B. As shown in Fig. 15, the output of demodulator ii is now fed through a condenser 58 shunted by a resistor 19. The time constant of condenser 1'3 and resistor 19 is so chosen that the voltage accumulated on condenser 18 will persist for a substantial part or" the period between consecutive transmitted pulses. This voltage may be as shown at 8| in Fig. 16.

With the modification of Fig. 15, signal storer it must be used. Thereupon, when a received pulse, such as 36a is produced, the electronbeam causes a bright spot to appear on the screen of the indicator 6, which persists, due to action of signal storer 44. Due to the variation of the voltage 8 i, this bright spot will move horizontally, in the illustration shown, for a distance determined by the instantaneous amplitude of the voltage ill at the instant the reflected pulse 38a is received, since the beam will be on all during the decay of voltage 81. The resulting indication will be as in Fig. 13A.

Accordingly, here again the length of the line segment indication will be inversely proportional to the reflection time and, accordingly, will indicate the proximity of the distant object.

It will be clear that in either or both Figs. 13 and 15, the wing voltage may be put on the vertical deflecting plates if desired, producing vertical line segment indications.

During spiral scanning and searching it. is desirable to be able to adjust the orientation of the spin axis I3 of the scanner and, hence, to change the space orientation corresponding to the pole 39 of the indication shown in Figs. 8A or 13A For this purpose, referring now to Figs. 17 and 5, scanner 1 is provided with azimuth and elevation servo devices, such as 82 and 8.3. rtspectively, adapted to actuate the scanner I about azi-v muth axis 21 and elevation axis 26, as shown in Fig. 5. These servo devices may be of any well known type adapted to position their outputs in accordance with suitable input voltages. Their details form no part of the present invention.

Also coupled to azimuth axis 21 is azimuth selfsynchronous transmitter 29. of. any. conventional type, and correspondingly coupled to elevation axis 26 is elevation transmitter 28. As is well known, these transmitters 29 and 28 are provided with alternating voltage of a suitable frequency, such as from source 43, and their respective outputs 84 and 86 correspond to the instantaneous orientation of spin axis I3 in azimuth and elevation.

Computer i is also provided with similar selfsynchronous devices 81' and 88 actuated respectively by the elevation and azimuth input settings of computer 1. These devices are connected to the outputs as and BS-oi scanner transmitters 2 9 and 28 and serve as synchronous transformers or signal generators as is well known, to produce in their outputs 89 and 9| alternating signal voltages corresponding in phase and magnitude to the sense and magnitude of relative displacement between the scanner orientation and the computer setting along the respective azimuth and elevation components. These outputs 89 and 9| control respective phase sensitive amplifiers 92- and Q3 which thereupon control the respective servos 82- and 830i the scanner l to reposition scanner l= into correspondence with the setting of computer i.

In this manner, by suitable control of computer 1, as by its manual orientation control 8, scanner i is caused to follow the orientation setting of computer i and its orientation may be thereby adjusted as desired.

The above action serves to set the orientation or the distant object or target in terms of its azimuth and elevation coordinates into computer I, when the scanner and target orientations coincide. For proper operation of computer I, however, to permit the determination of the correct gun aiming angles, it is also necessary to set therein data corresponding to the range of the target. For this purpose range pedal i0 is provided, which is actuated in the manner to be described.

As is well known, in a system of the present type using reflected pulses, the time interval or delay between the transmitted pulse and its corresponding reflected pulse is directly proportional to the distance or rangeof the reflecting object or target. Fig. 18 shows one type of indicating device, useful for setting this range data into computer I. Thus, control oscillator 32a. serves to energize and synchronize a suitable wave squaring device 32b of any desired type producinga square wave output having the same frequency as that'of control oscillator 32a. This output actuates a pulse generator 320 of conventional design suitable for deriving pulses for controlling the transmitter-modulator 3 I to produce the transmitted pulses already described with respect to Figs. 13 to 16. The received reflected pulses are passed by T-R box 33 in the manner already described, and actuate the receiver 4 to produce in its output, such as 94, a signal voltage having a wave shape similar to the envelope oi the received wave, such as 36 in Fig. 14.

Control oscillator 320. also feeds a variable phase shifter 86 of any suitable type whose output wave shape is then squared in a suitable wave squarer 91, which may be similar to wave squarer 32b, to derive a square wave output having a frequency identical with that of control oscillator 32a, but adjustable in phase position with respect thereto by means of phase shifter 95. It will thus be clear that the phase of the square wave output of wave squarer 91 is adjustable also with respect to the transmitted pulses and to, the received pulses. 

